Methods of and apparatus for guiding fabrics



Nov. 3, 1964 A. c. HICKS ETAL METHODS OF AND APPARATUS FOR GUIDING FABRICS Filed Sept. 14, 1962 8 Sheets-Sheet 1 I enlor hin/es I/I C KJ' Nov. 3, 1964 A. C.'HICKS ETAL 3,

METHODS OF AND APPARATUS FOR GUIDING FABRICS Filed Sept. 14, 1962 8 Sheets Sheet 2 y Wneys v- 1964 'A. c. HICKS ETAL 3,155,302

METHODS OF AND APPARATUS FOR GUIDING FABRICS Filed Sept. 14, 1962 8 Sheets-Sheet 3 Nov. 3, 1964 A. c. HICKS ETAL 3,155,302

METHODS OF AND APPARATUS FOR GUIDING FABRICS Filed Sept. 14. 1962 a Sheets-Sheet 4 Nov. 3, 1964 A. c. HICKS ETAL METHODS OF AND APPARATUS FOR GUIDING FABRICS Filed Sept. 14. 1962 8 Sheets-Sheet 5 Nov. 3, 1964 A. c. HICKS ETAL 3,155,302

METHODS OF AND APPARATUS FOR GUIDING FABRICS Filed Sept. 14, 1962 8 Sheets-Sheet 6 Nov. 3, 1964 A'. c. HICKS ETAL METHODS OF AND APPARATUS FOR GUIDING FABRICS Filed Sept. 14, 1962 8 Sheets-Sheet 7 ndikk il'sa' Nov. 3, 1964 A. c. HICKS ETAL 3,155,302

METHODS OF AND APPARATUS FOR GUIDING FABRICS Filed Sept. 14, 1962 8 Sheets-Sheet 8 By 21 m %rneys 3,1553% METHGDS GEE AND APPARATUS FUR GUHDINGFREQS Alfred (Iharles Hicks, Manchester, and Norman .Hambiey,

Middleton, Manchester, Engiand, assignors to Turner Brothers Asbestos Company Limited, Manchester,

England, a British cernpany Fiied Sept. 14, 1962, Ser. No. 223,782

i It Ulairns. (Ci. Ede-3) In various manufacturing processes it is important to maintain a moving length of a fabric in a straight path. At present it. is common to use a mechanical sensing device which,.when the fabric leaves the desired path, is disturbed by the fabric, together with a mechanism responsive to the mechanical sensing device and operative to apply a correcting force to the fabric. It is also common to use a photoelectric sensing device placed so that light directed towards it is intercepted by the fabric on a departure from the desired path.

A particularly difficult problem arises when several plies of fabric must be unrolled simultaneously to be formed into a multiply assembly, as in the manufacture of conveyor belting. It is obviously desirable that the sensing device should be as close as possible to the point where the plies are assembled together. Near to this point the plies will be so close to one another that it is impossiblefor space to be found for the sensing head of a mechanicalsensing device associated with each ply, and in any case it would be affected by more than one ply. With several plies it is essential to control the movement of each ply individually.

A photoelectric cell disposed to give a correcting signal when a ply interrupts an illuminating beam of light is also affected by each of several plies that may deviate from the correct path and is not able to distinguish which ply is at fault. 1

According to the invention each of two or more layersof moving fabric is constrained to follow a predetermined path by causing electric currents to flow in cyclic order in conductors each of which is incorporated in or carried on one layer offabric and which extend parallel to the centre lines the-reef and by electromagnetic induction to influence. a sensing device responsive to the transverse position of that conductor which is for the time being carrying current; and through a signal given by the sensing device applying a corrective force to that layer of fabric which incorporates or carries that conductor upon any deviation of that conductor from the predetermined path.

The current may be caused to flow in each conductor in various ways. Preferably this is done by connecting in a high-frequency circuit two plates each of which forms a. capacitor with the conductor. Again the current may be induced in the conductor by two transmitting coils located at different points along the length of the fabric in its direction of motion, each transmitting coil being supplied with a high-frequency alternating current. Yet again the current may be fed into the conductor through brush gear or the equivalent.

Thesensing device preferably comprises two coils with a common axis, electrically interconnected and mounted so that the fabric ply passes between them, the conductor lying in the common axis when the fabric is in the desired path. The sensing device may also comprise two coils mounted side by side so that the fabric passes above or below them with the conductor midway between them when the fabric is in the desired path.

Capacitance plates or other means through which the currents are caused to flow in the conductors are preferably individual to each conductor, a switching device being provided to complete each circuit in turn. The

United States Patent 0 3,155,302 Patented Nov. 3, 19%4 sensing device ispreferably common to all the con ductors, i.e. all the plies pass between the two coils of the device, or above or below the two coils, in accordance with the form of device used. Another switching device is provided to ensure that the signal applies the corrective force to the proper ply.

The conductor may be a metal wire, a filament or yarn of glass coated with metal, or graphite-impregnated yarn, any of which may be incorporated in the fabric as a warp thread during manufacture, preferably inthe selvedge in a Woven fabric. Again the conductor may be superimposed on the fabric after manufacture and secured to it. by a suitable adhesive or other fastening. Yet again, the conductor may be introduced intothe fabric, e.g. by moulding, duringthe mannfactureof the fabric. A

The invention includes apparatus for carrying out the method, this apparatus broadly comprising means for causing a high-frequency alternating current to flow in each conductor, in turn, a device common to all the conductors for sensing this current and means .by'which an output signal from the sensing device resulting from deviation of any conductor from the predetermined path is applied to mechanism for changing the path of the corresponding length of fabric. In addition the invention includes as a new article of manufacture a fabric having a single conductor extending throughout its length, preferably in the selvedge.

The preferred apparatus will now be described with reference to the accompanying drawings in which:

FIGURE 1 is a diagrammatic elevation; and

FIGURE 2 the corresponding plan of a plant for producing five-ply belting equipped with apparatus according to the invention for constrainingeach ply to move in a predetermined path;

FIGURE 3 is an elevation on a larger scale -of part of the plant;

FIGURE 4 is a partial plan corresponding to FIG- URE 3;

FIGURE 5 is a perspective view of a machine including guiding rolls;

FIGURE 6 is a diagram of the rolls in this machine;

FIGURE 7 is a section on the line VII VII in FIGURE 6; V

FIGURE 8 is an elevation of one end of. this machine;

FIGURE 9 is a front elevationof a sensing device common to all the plies; I

FIGURE 10 is a side elevation, and FIGURE 11 a plan, of the sensing device;

FIGURES 12 and 13 illustrate the principle on which the sensing device works;

FIGURE 14 is an electrical circuit diagram;

FIGURE 15 is a diagram showing another way of causing current to flow in a conductor;

FIGURE 16 is a diagram illustrating another form of sensing device;

FIGURE 17 is a section on the line XVIIX 'II in FIGURE 16; and

FIGURE 18 is a diagram showing a third way of causing a current to flow in a conductor.

In the plant shown in FIGURE 1 five rolls of fabric plies 1,2, 3, d and 5, each impregnated with polyvinyl chloride, are monnted in a creel 6. and unrolled from it to pass through a frame 7 in which path-straighteningrolls S are mounted, these rollsserving to direct each ply into or nearly into the desired path in a manner wellf known in the art. Next the plies passthrough a tcnsioning frame 9 comprising sets of rollers 10, each set engaging one ply. The plies pass onwards through a long heating chamber 11 in which they are maintained out of contact one another, and from which they pass to calender or nip rolls 12 by which they are formed into an assembly 13 and are united by the welding together of the polyvinyl chloride coatings. From the rolls 12 the welded assembly passes onto a conveyor belt 83 by which it is carried over a long fiat metal table 14, cooling during this movement. The movement is assisted by a pair of withdrawal rolls mounted in a frame 15. From the Withdrawal rolls the assembly is wound into a coil 16.

The parts of the plant so far described are not part of the present invention. The problem in producing such awelded assembly is to guide each ply so that all are in accurate register on arrival at the calender rolls 12. Ch emerging from the heating chamber the plies are very close together so that it is not possible to subject each to the action of any mechanical sensing and correcting device at this point.

In the invention, in which each ply has a conductor extending along the selvedge, metal flexible strips 17 17 are each mounted adjacent to one of the plies 1 5 in a space in the plant immediately after the tensioning frame 9, and act as capacitance electrodes. As shown in FIGURES 3 and 4 each strip 17' is held at one end by a holder 18' etc. mounted to slide along a bar 19' etc. carried by the frame 9, and at the other end by an adjustable holder 20' etc. carried by a bar 21 etc. fixed to a frame member 22' etc. of a guiding machine 23, which is placed just in front of the inlet to the heating chamber 11. The strips must be at the same distance fromthe centre line of the machine as the conductors, and of course this distance may vary, particularly with plies of different widths. The strips can be adjusted in position by sliding the holders 18 and 20 along the bars 19 and 21, and each can be held close to but preferably just out of contact with the ply beneath it by adjusting the holder 20.

Each strip 17' etc. is fed with high-frequency current through a flexible conductor 24' etc. The strip 17' and the conductor form one capacitor, and the conductor forms another with the table 14, which is electrically connected to earth.

The guiding machine 23 comprises two end frames 25 and 26 spanned both by main frame members 27 and by the members 22' etc. at the inlet side and similar members 28 etc. at the other side. The members 22 etc. are spaced apart from one another to leave gaps each for the passage of one ply, and the members 28 are similarly spaced apart. Longitudinal members 29' etc.

.join the members 22 etc. to the members 28 etc.

The machine 23 includes two pairs of correcting rolls 3t) and 31 for each ply, the pair 30 being mounted between the central members 29 and the end frame 25 and the other pair 31 between the members 29 and the end frame 26, and each pair when operating tending to move the fabric outwards from the centre line. As shown in FIGURES 6 and 7, one roll 32' etc. in-each pair is fixed in position, being journalled at one end in a bracket 33 carried by a bracket 34' fixed to the corresponding member 29", and being journalled at the other end in a bracket 35' fixed to the frame 25. The other roll 36 in each pair is journalled at each end in arms 37' that extend from sleeves 38 which are fixed to a rocking shaft 39'. Each rocking shaft-39 etc. passes through the frame 25, and outside the frame an arm 40 etc. is fixed to it. This arm carries a counter-weight 41' to balance the weight of the roll 36' and arms 37', and the armature 42 of a solenoid 43' is connected to it. When the solenoid is energized the shaft 39' is rocked to cause the roll 36' to bear on the roll 32 through the ply 1 and thus to change the path of movement of the ply.

To energize each solenoid 43 etc. a signal is required, and is given by a sensing device 44, which responds to the current flowing in the conductor in the ply and which is shown in FIGURES 9 to 11.

The sensing device comprises a laminated core 45 of magnetic metal which envelops all five plies of fabric and carries two pole pieces 46 and 47 opposite to one another,

each pole piece comprising a magnetic core with a winding round it. To allow adjustment of the position of the pole pieces for fabrics of different width, the core 45 is mounted to move transversely to the path of the plies, and infact it is carried by brackets 43 which extend forwards from a transverse carriage 4? that is mounted to slide in brackets 58 fixed to the outlet end of the chamber 11. The transverse movement of the carriage 49 is effected through a rack chain 51 which is fixed to the carriage and engaged by a sprocket 52 which can be turned through a hand wheel 53, a position indicator 89 being provided to assist in the proper adjustment. To increase the range of adjustment without causing the sensing device to project too far laterally a duplicate coil 45a with pole pieces 46a and 47a is provided, these pole pieces being nearer to the centre line of the whole plant than the pole pieces 46 and 47 and used with narrower fabrics.

FIGURES 12 and 13 show the principle on which the sensing device works. The conductor in the fabric is shown at 54. The coils of the pole pieces 46 and 47 are connected in series and their combined output is fed into a conventional A.C. amplifier 81. The current in the conductor 54 is assumed to be instantaneously flowing into the plane of the paper, resulting in an electromagnetic flux conventionally represented by clockwise concentric circles 55. It will be seen that when the conductor 54 is to the left of the sensing coils, as shown in FIGURE 12, the flux direction between the coils is downwards from the coil 46 to the coil 47 and if the conductor is to the right of the coils, as shown in FIGURE .13, the flux direction is upwards from the coil 47 to the coil 4-6. In the first case the instantaneous direction of the current through the amplifier circuit is anticlockwise whilst in the latter case this flow is reversed. The sensing device is adjusted so that when the fabric is following the desired path the conductor 54 lies precisely on the centre line of the pole pieces 46 and 47. Under these conditions the amplifier input will be zero. Should the conductor leave the desired path, the amplifier will receive an input current, the instantaneous direction of which is dependent on whether the conductor lies to the right or the left of the desire path.

It will be seen that the sensing device is common to all the plies and will therefore feed an error signal to the amplifier 81 if any conductor through which current is flowing is out of path. To cause this error signal to lead to energisation of the proper solenoid in the guiding machine it is necessary first to cause current to flow in only one conductor at a time and second to provide means for selectively transmitting the amplified error signal from the amplifier 81 to the proper solenoid. The way in which the desired result is obtained is shown by FIG- URE 14, in which for the sake of simplicity only two plies and the associated solenoids are shown.

The currents are generated by a generator 56 and transmitted through a rotary selector 57, driven by a timing motor 58, to the strips 17' etc. The selector 57 has segments 59' etc. corresponding to the plies and thus ensures that acurrent flows in each conductor 54 etc. in turn.

The output from the amplifier 81 is fed into a conventional phase-sensitive rectifier 60 which also receives a reference signal from the generator 56. The final output from this system is thus a direct-curent error signal, the polarity and value of which are a measure of the sense and magnitude of any displacement of the fabric from its desired path. This error signal passes through a second rotary selector 61, also driven by the motor 58, and having segments 62 etc. corresponding to the five plies. Assuming that current is flowing in the conductor 54', the error signal is fed through the segment 62 into a retaining capacitor 63'. The output impedance of the rectifier 60 is very low and hence the capacitor 63 is charged almost instantaneously as soon as the wiper arm of the selector 61,makes the necessary contact. This capacitor now controlsthe correcting operation untilsuch time as it is. charged again on the next revolution of the wiper arm. The polarity ofthe voltage across the capacitor 63' is dependent on the sense of the error in the path of the fabric and, according to this polarity, the voltage will cause a small current to pass through either a diode 64 and a transistor power amplifier 65 or through a corresponding diode 66 and amplifier 67, The power amplifier 65 energises the solenoid 43 to engage the roll I 36, with the roll 32 if the fabric should move to the right of the. desired path as seen in FIGURE 2. If the fabric should move to the, left, the signal passes through the amplifier 67, to energise the corresponding solenoid 68 (not shown in FIGURES 5 to 8) on the other side of the guiding machine.

The input impedance of each power amplifier is very high, being approximately 100,000 ohms, so that the capacitor 63 will discharge slowly. Thus an error signal, which charges the capacitor almost instantaneously when the selector 61 makes the necessary contact, will result in a corrective action which continues until the next time the switch makes contact. In practice, this means that the speed of the switching and electronic circuits is not limited by the inertia of the solenoid and mechanical systems, so that although it may take many revolutions of the selector before any error is finally corrected, the actual transverese motion of the fabric will be continuous. A switching speed of fifty cycles per second is found to be satisfactory. In order to prevent hunting, the component values of the elements of the circuit are made such that if the error in the path of the fabric is less than inch, the resulting voltage on the capacitor 63 is insufficient to energise a solenoid.

A similar capacitor 63 and circuit for the second ply are shown in FIGURE 14, and it will be understood that there are three further such capacitors and circuits for the remaining plies.

Many modifications may be made. For instance the rotary selectors shown may be replaced by static electronic switches.

Again the current may be caused to flow in each con- (luctor in the way diagrammatically illustrated by FIG- URE 15, which shows only one ply. Here a transmitting coil 68 encircles the fabric at a point well ahead of the heating chamber and a similar transmitting coil 69 is placed beyond the rolls 12. The circuit for the induced current is completed through two capacitors formed by metal plates 70 and 82 placed near each end of the length of fabric which is being controlled and adjacent to the edge of the fabric and to the conductor 54. If the transmitting coils are supplied with power a current will be induced in the conductor.

FIGURE also shows another form of sensing device, which is shown in more detail in FIGURES 16 and 17. This comprises two sensing heads '71 and 72, located just before the point at which the fabric enters the rolls 12. Each head consists of a rectangular ferrite core '73 which carries a coil 74 on one limb. The opposite limb of the core has a central air gap 75 and this limb is placed just above the fabric and parallel to the conductor. The two sensing heads together form a sensing device in which the two coils are side by side with their aXes parallel both to each other and to the desired path of the filament. n The device is so located that this path lies below the coils and at a precisely equal distance from each.

FIGURE 18 diagrammatically shows yet another way of casuing current to flow in a conductor. In it the fabric is unwound from a roll '75 and rewound on a roll 76. The rolls 75 and 76 are made of metal and are thus in electrical contact with the conductor 54. Current from a generator 77 is fed into the filament through brushes 78 and 79 which bear on the rolls '75 and 76.

We claim:

1. A method of constraining each of at least two layers of moving fabric to-follow a predetermined path comprising the following stepsz- 5 (a) causing electric currents to flow in cyclic order in conductors, each of which is carried by one layer of fabric and which extend parallel to the centre lines thereof;

(b) influencing by electromagnetic induction a sensing device responsive .to the transverse position of that conductor which is for the time being carrying current; and

(c) applying, through a signal given by the sensing device, a corrective force to that layer of fabric which carries that conductor upon any deviation of that conductor from the predetermined path.

2. An apparatus for guiding a plurality of lengths of moving fabnic in a predetermined path, each length carrying a conductor that extends parallel to the centre line of the fabric, comprising the following integers:

(a) means for causing a high-frequency alternating current to flow in each conductor in turn;

(b) a device common to all the conductors for sensing this current;

(0) means by which an output signal from the sensing device resulting from deviation of any conductor from the predetermined path is applied to mechanism for changing the path of the corresponding length of fabric to correct any such deviation.

3. An apparatus according to claim 2 in which the means for causing the current to flow in each length include input and output capacitors each formed by a plate and the conductor.

4. An apparatus according to claim 3 in which the plates of the input capacitors are formed by strips extending parallel to the conductors, and a metal table over which all the lengths move forms the plate of each output capacitor.

5. An apparatus according to claim 4 in which the strips are mounted :to move transversely to cooperate with fabrics of different width.

6. An apparatus according to claim 2 in which the sensing device includes a core embracing all the lengths of fabric and two coils with a common axis mounted so that 45 each conductor passes between them when it is in the correct path.

7. An apparatus according to claim 6 in which the sensing device is carried by a transversely movable frame.

8. An apparatus according to claim 2 in which the mechanism for changing the path of a length of fabric comprises a pair of rollers inclined to the path of movement of the fabric and a solenoid operative on receiving a signal from the sensing device to cause the rollers to grip the fabric.

9. An apparatus according to claim 8 including interconnected seleotors one operative to connect each conductor in turn to the sensing device and the other operative to transmit the signal from the sensing device to the solenoid associated with the fabric that carries the same conductor.

10. An apparatus for guiding a plurality of lengths of moving fabric in a predetermined path, each length carrying a conductor that extends parallel to the centre line of the fabric, comprising the following integers:

(a) a metal electrode for each of said lengths of fabric forming an electrical capacitance with the conductor in said layer;

(b) a metal electrode common to all the said lengths of fabric forming an electrical capacitance with each of the conductors;

' (c) a highfrequency signal generator electrically connected to said electrodes;

(d) two sensing coils with a common axis, electrically interconnected and mounted so that the fabric passes between them, said conductor lying on said common axis when the fabric is in the desired path;

(e) a Laminated core surrounding the lengths of fabric and carrying said sensing coils, the core being capable of transverse movement so as to accommodate varying widths of fabric;

(f) a mechanism for changing the path of each of said lengths of fabric comprising a pair of rollers inclined to the path of movement of the length of I fabric and a solenoid operative on receiving a signal from said sensing coils to cause the rollers to grip the fabric.

(g) synchronous switching means arranged so as to 8 cause a current to flow in each of said conductors in cyclic order and to direct the signal from said sensing coils so as to influence that solenoid which will cause a correction to be applied to that length of fabric which carries that conductor which is for the time being carrying current.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD OF CONSTRAINING EACH OF AT LEAST TWO LAYERS OF MOVING FABRIC TO FOLLOW A PREDETERMINED PATH COMPRISING THE FOLLOWING STEPS:(A) CAUSING ELECTRIC CURRENTS TO FLOW IN CYCLIC ORDER IN CONDUCTORS, EACH OF WHICH IS CARRIED BY ONE LAYER OF FABRIC AND WHICH EXTEND PARALLEL TO THE CENTRE LINES THEREOF; (B) INFLUENCING BY ELECTROMAGNETIC INDUCTION A SENSING DEVICE RESPONSIVE TO THE TRANSVERSE POISITION OF THAT CONDUCTOR WHICH IS FOR THE TIME BEING CARRYING CURRENT; AND (C) APPLYING, THROUGH A SIGNAL GIVEN BY THE SENSING DEVICE, A CORRECTIVE FORCE TO THAT LAYER OF FABRIC WHICH CARRIES THAT CONDUCTOR UPON ANY DEVIATION THAT CONDUCTOR FROM THE PREDETERMINED PATH. 